Lubricants containing lead dithiophosphates



United States Patent M 3,0811%1 I V I LUBRICANTS CO, ,TAINING LEAD BITE-I- PHGS'PHATES FrankA. Stuart, Oriiidia, and Chester D. Gordon, Richmore, care, assignors to California Research Corporation, San Francisco Califi, a corporation of Delaware N0 Drawing. Filed Au'g..25, 1960, Ser. No. 51,803 10 Claims. (Cl. 252-32.7)

I This invention pertains to lubricating oil compositions having incorporated therein a combination of a metal-free detergent and a lead salt of a dithiophosphoric acid. These particular lubricating oil compositions have beneficial {properties which are described further in detail herein.- b'elow. I I

Present-day internal combustion engines operate athigh speeds and high compression ratios. When used in the so-called city stopandgo driving, which includes the greater part of the driving conditions for a large percent! age of todays automobiles, the internal combustion engines do not reach the most efficient operating temperature. Under city driving conditions, large amounts of partial oxidation products are formed, and reach the crankcase of the engine by blowing past the piston rings. Most of these partial oxidation products are oil-insoluble, tending to form deposits on the various operating parts of the engine, such as thepistons, piston rings, etc. For the purpose of preventing the deposition of these products onthe various engine parts, it is necessary to incorporate detergents in the lubricating oil compositions, thus, keeping these oil-insoluble products highly disperse-d in a condition unfavorable for deposition on the metal parts of engines.

For the most part, the various detergents which are added to crankcase oils to reduce this formation of sludges and varnishes are metal organic compounds, particularly those compounds wherein the metal is linked to an organic group through an oxygen atom. Although these metal containing organic compounds have some effectiveness as detergents for dispersing the precursors of deposits within the oil itself rather than permitting them to form added deposits on the engine parts, they have the disadvantage of. forming ash deposits in the engine. These ash deposits .lower engine performance by fouling spark plugs and valves, and contributing to preig-nition. More recently, lubricating oil compositions have appeared on the market which contain various ashless, metal-free detergent compositions to eliminate the formation of such ash deposits in the engines. Theashless detergents having particularly "high molecular weights in the range of about 250,000 to about 1,000,000 are solublein lubricating oil compositions .invarying degrees. Although ashless metal-free detergents of high molecular weight are extremely effective as addi- 'tives in lubricating oil compositions, it is necessary to use corrosion inhibitors in combination therewith.

For the most part, todays lubricating oil compositions contain numerous zinc salts as CQIIOSlOlTlil'lhibllIQlS. Particular zinc salts include the zinc salts of dithiophosphoric acids. Representative of ,suchzinc dithiophosphatesare thezinc salts of -di(alkylphenyl) dithiophosphoricacids, alkyl, alkylphenyl dithiophosphoric acids, dialkyl dithiophosphoric acids, and mixed dialkyl dithioph'osphoric acids wherein the alkyl radicals are diiferent, one being of lower molecular weight than the other.

In combination with the high molecular weight polymeric ashless, metal-free detergents the zinc dithiophosphate corrosion and oxidation inhibitors cause-a formof deposit formation which is called lead paint. This deposit-appears to result from some type of reactionbetween the high molecular weight type detergents and the .zinc metal of the dithiophosphat'e "to reduce taesgianm streamer the polymeric detergents in the lubricating oil composition, cau sing the polymers to drop out of solution. Ehis phenomenon increases as the polarity of the ashless metal-free detergents increases; that is, this phenomenon increases as the oil solubility of these detergents decreases. On dropping out of the solution from the oil, these droplets form sticky, resinous deposits. These sticky deposits then coagulate the lead halides which are blown past the piston rings from the combustion chamber to give the socalled lead paint deposits. These lead paint deposits cause engine failure by oil-ring clogging and bearing .WiPiInIIg I I I I I II I herefore, it is a particular object of this invention to provide a metal dithiophosphate corrosion and oxidation inhibitor to be used in combination with ashless metal-free detergents of high molecular weight to inhibit the formation of lead deposits in the engine parts. I I I I I In accordance with this invention, it has been discovered that lubricatin g oil compositions which effectively inhibit lead paint formation are obtained by incorporating in oils of lubricating viscosity the combination of certain high molecular weight ashless metal-free polymeric detergents and lead salts of dithiophosphoric acids. I No only do the metal-free detergents and the lead dithiophcsphates result in the formation of lubricating oils which inhibit lead paint formation, but bearing wiping is inhibited. I I

. The ashless metal-free polymeric detergents which are particularly effective herein include those having molecular weights I in the range of 250,000 through about 1,000,000. I S uch ashless metal-free detergents include the Acryloid 9l7 A cryloid 966 (which are sold by the Rohm and Haas Company), ashless polymeric metal-free detergents described in U.S. Patent No. 2,892,783, etc.

Of particular benefit herein in combination with lead dithiophosphates are the polymeric high molecular weight detergents described in U.S. 2,892,783. Briefly, these metal-free detergents are oil-soluble polyglycol substituted polymers of at least one monomer containing a single polymerizable ethylenic bond and from about 40% to about 96%, by weight, of hydrocarbon oil-solubilizing groups and from about 4% to about 60%, by weight, of polyglycol groups. The oil-solubilizing groups include the aliphatic and cycloaliphatic groups containing from 4 to 12 carbon atoms each, and the polyglycol groups are polyalkylene glycols and monoalkyl ethers having from 2 to 7 carbon atoms in each alkylene group. The polyglycols have at least 5 alkylene oxide units each and are attached by a single thermally stable organic linking group -to the polymer.

Example I hereinbelow illustrates the formation of .a particularly effective high molecular weight ashless metal- .free detergent which in combination with a zinc dithiophosphate forms lead deposits, 'but when the zinc is replaced With a lead dithiophospha-te, the lead paint formation is remarkably reduced.

EXAMPLE I A mixture of 24.5 grams of a 40% benzene solution of a lauryl capped polyethylene glycol methacrylate having a molecular weight of about 1800, 29.4.grams of oxotridecyl methacrylate, l6.6 of lauryl methacrylate, 2 6,3 gramsjof stearyl metlracrylate, and 43.5 grams of benzene was blended in a 500 inl.,glass reaction flask. The vessel was purged with nitrogen, after which the I 1.0 ml, of a solution of ,1 gram of azo bis isobutyronitrile in 100 .ml of benzene was added as the polymerization initiator.

(1.0 ml. of this solution was added at 15 minute intervals during the polymerization reaction.)

,To-the aboveblend, during a period of; hours, was added a solution consisting of 7.3 grams of oxotridecyl ne hacryat ai grains oflauryl methacrylate, 6.5 grams of stearyl methacrylate, and 12.6 grams of benzene. The polymerization reaction was continued for an additional 2 hours.

After the 4-hour polymerization period, diluent oil was added to give a 40% solution of the polymer in oil. The benzene was removed by distillation. The molecular weight of the polymer was about 450,000.

EXAMPLE II A three-necked flask fitted with a stirrer, thermometer, refiex condenser, and dropping funnels was charged with 29.6 grams (0.35 mol) of hexene-l. The monomer was stirred and heated to reflux temperature of 146 F. A monomer mixture consisting of 89 grams (0.35 mol) of lauryl methacrylate, 1.2 grams (0.015 mol) of methacrylic acid, and 61.2 grams (0.059 mol) of dodecylcapped polyethylene glycol methacrylate (molecular weight 1,034), in 30 cc. of benzene was added to the refluxing hexene simultaneously with the addition of the catalyst solution. After the addition of 100 cc. of the monomer mixture and approximately 0.45 gram of benzoyl peroxide in cc. of benzene over a period of 2 hours, no polymerization was observed. During the course of addition, the temperature gradually rose, and after another 2 hours the maximum temperature reached was 187 F. Considerable thickening occurred during this time and it was necessary to add xylene valent in small portions at intervals to facilitate stirring. The mixture was kept at 190 F. for another 3 hours. At this point, 177 grams of lubricating oil were added. The solvent and unreacted hexane, lauryl methacrylate and methacrylic acid were distilled from the mixture to give 140 grams of polymer as a 44% concentrate.

The lead salts of esters of dithiophosphoric acids are represented by the following formula:

it 2 wherein R and R may be alkyl, aryl, alkaryl, aralkyl, or cyclic nonbenzoid hydrocarbon radicals each containing from 1 to 25 carbon atoms. It is preferred that the R radical contains from 1 to 4 carbon atoms, and that the R radical contains from 5 to 25 carbon atoms. R and R may or may not be identical.

In the practice of this invention, it is preferred to use lead salts of mixed esters of dithiophosphoric acids wherein R is derived from an alcohol containing no more than 4 carbon atoms; for example, methyl, ethyl, propyl, isop-ropyl, butyl, see-butyl, tertiary butyl, etc.; and wherein R is derived from alcohols containing from 5 to 18 carbon atoms, including amyl, hexyl, methylisopropylcarbinol, heptyl, isoheptyl, 2-ethylamyl, octyl, isooctyl, 3-ethylhexyl, Z-propylamyl, decyl, undecyl, dodecyl, hexadecyl, octadecyl, etc.

Examples of R and R' when these are the same include the following radicals: octyl, decyl, dodecyl, tetradecyl, hexadecyl, oetadecyl, hexylphenyl, decylphenyl, dodecylphenyl, h-exadecylphenyl, cctadecylphenyl, etc.

The esters of dithiophosphoric acids used in the preparation of the lead salts of this invention include butyl,

amyl dithiophosphoric acid; methyl, hexyl dithiophosphoric acid; ethyl, hexyl dithiophosphoric acid; butyl, methylisobutylcarbinol dithiophosphoric acid, butyl, heptyl dithiophosphoric acid; butyl, decyl dithiophosphoric acid; butyl, isoheptyl dithiophosphoric acid; butyl, octadecyl dithiophosphoric acid; dioctyl dithiophosphoric acid; diheptyl dithiophosphoric acid; dihexadecyl dithiophosphoric acid, dioctadecyl dithiophosphoric acid, di(octadecylphenyl) dithiophosphoric acid, etc.

Lubricating oils which can be used as base oils include a wide variety of lubricating oils, such as naphthenic base, paratfin base, and mixed base lubricating oils, other hydrocarbon lubricants, e.g., lubricating oils derived from coal products, and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc., and the mixtures thereof), alkylene oxide-type polymers (e.g., propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing the alkylene oxide in the presence of water or alcohols, e.g., ethyl alcohol, dicarboxylic acid esters (such as those which are prepared by esterifying such dicarboxylic acids as adipic acid, azelaic acid, subcric acid, sebacic acid, alkanol succinic acid, fumaric acid, maleic acid, etc., with alcohols such as butyl alcohol, hexyl alcohol, 2- ethyl hexyl alcohol, dodecyl alcohol, etc.) liquid esters of acids of phosphorus, alkyl benzenes (e.g., monoalkyl benzene such as dodecyl benzene, tetradecyl benzene, etc., and dialkyl benzenes (e.g., n-nonyl 2-ethyl hexyl benzene); polyphenyls (e.g., biphenyls and terphenyls), alkyl biphenyl ethers, polymers of silicon (e.g., tetraethyl silicate, tetraisopropyl silicates, tetra(4-methyl-2-tetraethyl) silicate, hexyl (4-methyl-2-pentoxy) disiloxane, poly(methyl) siloxane, poly(methylphenyl) siloxane, etc. Synthetic oils of the alkylene oxide-type polymers which may be used include those exemplified by the alkylene oxide polymers.

The above base oils may be used individually or in combinations thereof, wherever miscible or wherever made so by the use of mutual solvents.

The high molecular weight ashless metal-free detergents used in combination with the lead dithiophosphates according to this invention are used in amounts of 0.1% to 10%, by weight, preferably 0.5% to 5%, by weight.

The lead dithiophosphates are used herein in amounts sufficient to inhibit lead paint formations in lubricating oil compositions containing high molecular weight ashless metal-free detergents. Such amounts include from 0.3% to 3%, by weight, preferably from 0.8% to 2.0%, by weight.

The test data submitted hereinbelow in Tables I and II show the effectiveness of the lead dithiophosphates in inhibiting lead paint formation on metal surfaces in internal combustion engines using lubricating oils containing ashless metal-free detergents.

Zinc dithiophosphate A was the zinc salt of a di(alkylphenyl) dithiophosphoric acid wherein the alkyl radicals were derived from propylene polymers containing an average of about 12 carbon atoms. Zinc dithiophosphate B was the zinc salt of a mixed dialkyl dithiophosphoric acid wherein one of the alkyl radicals contained 4 carbon atoms and the other alkyl radical contained 6 carbon atoms.

Lead dithiophosphate A was a lead salt of the same di(alkylphenyl) dithiophosphoric acid described herein above for the z'nc dithiophosphate A.

Lead dithiophosphate B was the lead salt of a mixed diorgano dithiophosphoric acid wherein the organo radicals were on the average mol percent methylisobutylcarbonyl radical and 20 mol percent alkylphenyl radicals,

wherein the alkyl radical was derived from propylene polymers containing an average of about 12 carbon atoms.

Lead dithiophosphate C was the lead salt of diorgano dithiophosphoric acid wherein the organo radicals comprise 80 mole percent of methylisobutylcarbonyl radical and 20 mol percent of a radical derived from oxodecyl alcohol.

Lead dithiophosphate D was the lead salt of the same dithiophosphoric acid described hereinabove for zinc dithiophosphate B.

The dithiophosphates were used in amounts expressed as millimoles per kilogram (i.e., mM./kg.), based on the metal content of the dithiophosphate.

The ashless metal free detergent used was prepared as; described hereinabove in Example I, the molecularweIght being approximately 450,000.

In the lead paint test, the lubricating oil compositions were used in a 6-cylinder Chevrolet engine operating at 2300 1 m. at 50 brake horse power with'the -oil sump temperature at 190 F.for a period of :36-hours with an oil change at 24- hours. Thele'ad deposits were measured on 115 engine parts, and the leadxpaint rating was ex- .pressed on a scaleof for clean metal parts to 01m a "completely "covered metal spot, with the tabulatedrating being an average forthe '15 engine .p'art values.

Table I 'Poly'ineric Metal Ditliiopho'sphat'e, Detergent *mMJlrg.

Lead Paint. Wt. Zn Pb Rating Ratlo Percent 2 i A B A 13 54:1 2.8 0.0 0.0 0.0 0.0 9. 5 1 28 .6 0-10 0 0' 'l 0 -,8= 54:1 2.8 12 '0.0 0.0 0.0. 8.3 54:1 2.8 0.0 18 0.0 0.0 7-.8 33:1 2.8 0.0 is- 0.0 0.0 7-.8 a so as 0.0 0.0 0.0 18 9.3 3321' 1.0 0.0 0.0 0.0 8.4 .3311 1.0 0,0 0.0 0.0 15 0.4 33:1 1.0 12 0.10 0.0 0.0 8.0 3311 1.0 0. 0 0. 0 12 0.0 0.1.

The 'alkyl methacrylatelpolyglycol mol ratio of polymer. The polyglycolpolymer molecular weight; was 1600. Based on dry polymer.

Table II hereinbelow further illustrates the effectiveness of the lead dithiophosphates-in inhibiting lead paint deposits in engines wherein the lubricating oil .composi .tion contained high molecular weight ashless metal-free detergents, and in addition, presents weartest data obtained under L-4 test conditions.

The L-4 engine test, which is fully described in the CRC Handbook, 1946 edition, Coordinating Research Council, New York, New York, is designed to evaluate fthe'bearing corrosion characteristics and high temperature detergency of-lubrica'ting oil compositions. The detergency characteristics are rated by the piston varnish rating wherein a'value of 10 represents a'cle'an piston, and a value of 0 represents a piston heavy with varnish, and values intermediate between 0 and 10 rate the varnish deposits correspondingly. The L-4 test was run for 36 hours unless otherwise noted.

The polymeric detergent and the metal dithiophos- .phates are the same as-those described hereinabovefor Table I.

.Table II Polymeric Metal Dithiophosphate, Detergent mM./kg.

Lead. Bea'rin ,Paint Wt. Pb Rating Loss Ratio Wt. Zn, Mgs.

Pen -A cent A B C D 33:1 7.5 ,18 0.0 0.0 0.0 0.0 7.8 33:1 1.5 12 0.0 0.0 0.0 0.0 8.6 33:1 2.5 6 -00 0.0 0.0 0.0 -9.0 33:1 6. 5 0. 0 0. 0 0. 0 "0:0 0. 0 0. 5 .3311 0.5- 0.0 0.0 0.0 0.0 s a 9.3 3311 7 0.0 0.0 0.0 0. 0 18 33:1 2.5 0.0 12 I 0.0 0.0 0.0 9 1 The alkyl methacrylate/polvglycol mol ratio of polymer. The

polyglycol polymer molecular weight was 1600.

Based ondry polymer. 1 Average of 2 runs.

72 hours.

We claim: I

1. A lubricant composition comprising a major proportion of an oil of lubricating viscosity and from 0.01% to 10%, by weight, of an oil-soluble polyglycol substituted polymer of at least 1 'monomer said monomer containing a single polymerizable ethylenic bond and said polymer containing from about 40% to about 96%, by weight, of hydrocarbon oil-solubilizing groups from saidpolyrnerized monomer and from about 4% to about 60%, by weight, of polyglycol groups, said oil-solubilizing groups being aliphatic groups containing at least 4 carbon atoms, said polyglycol groups being selected from the class consisting of polyalkylene glycols and monoallgyl ethers thereof having from 2'to 7 carbon atoms in-each alkylene group, said polymer being substantially saturated and having a totalmolecular weight of at least 250,000, said polyglyool's having at least five alkyle ne oxide units each and being attached by a single thermally stable organic linking group to said polymer'and from 0.3% to 3%, by weight, of an oiljsoluble lead salt of a dithiophosphoric acid of :the formula wherein R and R are radicals selected from the group consistingof alkyl and alkaryl radicals, each containing from 1 to 25 carbon atoms.

2. A lubricant composition comprising a major proportion of an oil of lubricating viscosity and from 0.5% to 5%, by Weight, of an oil-soluble polyglycol substituted polymer of at least 1 monomer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about to about 96%, by weight, of

hydrocarbon oil-solubilizing groups from said polymerized monomer and from about 4% to about 60%, by weight, of polyglycol groups, said oil-solubiliz'i'rig groups being aliphaticgroups containing from 4 to 12 carbon atoms each, said polyglycol groups being selected from the class consisting of olyalkylene fgl'yeols and monoalkyl others thereof having from 2 to 7 carbon atoms in each alk'y'lene group, said polymer being substantially saturated and having a total molecular weight of at least 250,000, said polyglycols having .at least five alk'ylene oxideunits each "and being attachedby a'single thermally stable organic linking group to'sai'd polymer and from 0.3% to 3%, by weight, of anoil soluble lead salt of a dithiophosphoric acid of the formula Kel -is Pb wherein R andR' areradicals's'elected from the group consisting ofbalkyl and alkaryl radicals, each containing from l-to 25 carbon atoms.

3. Alubricant composition "comprising a major proportion'of an oil oflubr'icati'ng' viscosity and from 0.5% "to 5%, by weight, of an oil-soluble polyglycol substituted polymer of at least 1 m0n0mer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about 40% to-about 96%, by weight, of hydrocarbon oil-solubilizing groups from said polyrnerized monomer and'from -about 4% to about by 7 weight, of polyglycol groups-,-said oil=solubilizinggroups being aliphatic groups containing -from 4 to 12 carbon atomseach, saidpolyglycolgroupsbeingselected from the class consisting of -polyalkylene (213 6018 and monoalkyl -"ethers thereof .havingfro'm 2-167 carbon atoms in each 7:; organic linking group tosaid polymer "afid.fl'Qm 0.8%

to 2%, by weight, of an oil soluble lead salt of a dithiophosphoric acid of the formula wherein R and R are radicals selected from the group consisting of alkyl and alkaryl radicals, each containing from 1 to 25 carbon atoms.

4. A lubricant composition comprising a major proportion of an oil of lubricating viscosity and from 0.5% to 5%, by weight, of an oil-soluble polyglycol substituted polymer of at least 1 monomer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about 40% to about 96%, by weight, of hydrocarbon oil-solubilizing groups from said polymerized monomer and from about 4% to about 60%, by weight, of polyglycol groups, said oil-solubilizing groups being aliphatic groups containing from 4 to 12 carbon atoms each, said polyglycol groups being selected from the class consisting of polyalkylene glycols and monoalkyl ethers thereof having from 2 to 7 carbon atoms in each alkylene group, said polymer being substantially saturated and having a total molecular Weight of at least 250,000, said polyglycols having at least five alkylene oxide units each and being attached by a single thermally stable organic linking group to said polymer, and from 0.8% to 2%, by weight, of a lead salt of dithiophosphoric acid of the formula 11' 2 wherein R and R are radicals consisting of 80 mol percent of methylisobutyl carbinol, and 20 mol percent of an alkylphenyl group wherein said alkyl radical is derived from propylene polymers containing an average of 12 carbon atoms.

5. A lubricant composition comprising a major proportion of an oil of lubricating viscosity and from 0.01% to by weight, of an oil-soluble polyglycol substituted polymer of at least 1 monomer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about 40% to about 96%, by weight, of hydrocarbon oil-solubilizing groups from said polvmerized monomer and from about 4% to about 60%, by weight, of polyglycol groups, said oil-solubilizing groups being aliphatic groups containing from 4 to 12 carbon atoms each, said polyglycol" groups being selected from the class consisting of polyalkylene glycols and monoalkyl ethers thereof having from 2 to 7 carbon atoms in each alkylene group, said polymer being substantially saturated and having a total molecular weight from 250,000 to 1,000,000, said polyglycols having at least five alkylene oxide units each and being attached by a single thermally stable organic linking group to said polymer and from 0.3% to 3%, by weight, of an oil soluble lead salt of a dithiophosphoric acid of the formula tuted polymer of at least 1 monomer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about 40% to about 96%, by weight, of hydrocarbon oil-solubilizing groups from said polymerized monomer and from about 4% to about 60%, by weight, of polyglycol groups, said oil-solubilizing groups being aliphatic groups containing from 4 to 12 carbon atoms each, said polyglycol groups being selected from the class consisting of polyalkylene glycols and monoalkyl ethers thereof having from 2 to 7 carbon atoms in each alkylene group said polymer being substantially saturated and having a total molecular weight from 250,000 to 1,000,000, said polyglycols having at least five alkylene oxide units each and being attached by a single thermally stable organic linking group to said polymer and from 0.3% to 3%, by weight, of a lead salt of a dithiophosphoric acid of the formula ii 2 wherein R is an alkyl radical containing from 1 to 4 carbon atoms, and R is an alkyl radical containing from 5 to 25 carbon atoms.

7. A lubricant composition comprising a major proportion of an oil of lubricating viscosity and from 0.01% to 10%, by weight, of an oil-soluble polyglycol substituted polymer of at least 1 monomer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about 40% to about 96%, by weight, of hydrocarbon oil-solubilizing groups from said polymerized monomer and from about 4% to about 60%, by weight, of polyglycol groups, said oil-solubilizing groups being aliphatic groups containing from 4 to 12 carbon atoms each, said polyglycol groups being selected from the class consisting of polyalkylene glycols and monoalkyl ethers thereof having from 2 to 7 carbon atoms in each alkylene group, said polymer being substantially saturated and having a total molecular weight from 250,000 to 1,000,000, said polyglycols having at least five alkylene oxide units each and being attached by a single thermally stable organic linking group to said polymer and from 0.3% to 3%, by weight, of a lead salt of a dithiophosphoric acid of the formula l RO-li-S- Pb wherein R and R' are alkylphenyl radicals, said alkyl radical being derived from propylene polymers containing an average of about 12 carbon atoms.

8. A lubricant composition comprising a major proportion of an oil of lubricating viscosity and from 0.5% to 5%, by weight, of an oil-soluble polyglycol substituted polymer of at least one monomer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about 40% to about 96%, by Weight, of hydrocarbon oil-solubilizing groups from said polymerized monomer and from about 4% to about 60%, by weight, of polyglycol groups, said oil-solubilizing groups being aliphatic groups containing from 4 to 12 carbon atoms, said polyglycol group being a polyalkylene glycol having from 2 to 7 carbon atoms in each alkylene group, said polymer being substantially saturated and having a total molecular weight of about 450,000, said polyglycols having at least five alkylene oxide units each and being attached by a single thermally stable organic linking group to said polymer and from 0.8% to about 2.0%, by weight, of a lead salt of a dithiophosphoric acid of the formula wherein R and R are mixed alkyl radicals containing on the average mol percent methyl,-isobutyl carbonyl radical and 20 mol percent alkyl phenyl radicals, wherein the alkyl radical is derived from propylene polymers containing an average of about 12 carbon atoms.

9. A lubricant composition comprising a major proportion of an oil of lubricating viscosity and from 0.5% to by weight, of an oil-soluble polyglycol substituted polymer of at least one monomer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about 40 to about 96%, by weight, of hydrocarbon oil-solubilizing groups from said polymerized monomer and from about 4% to about 60% by weight, of polyglycol groups, said oil-solubilizing groups being aliphatic groups containing from 4 to 12 carbon atoms, said polyglycol group being a polyethylene glycol, said polymer being substantially saturated and having a total molecular weight of about 450,000, said polyglycols having at least five alkylene oxide units each and being attached by a single thermally stable organic linking group to said polymer and from 0.8% to about 2.0%, by weight, of a lead salt of a dithiophosphoric acid of the formula wherein 'R and R' are mixed alkyl radicals containing on the average 80 mol percent methyl, isobutyl carbonyl radical and 20 mol percent alkyl phenyl radicals, wherein the alkyl radical is derived from propylene polymers containing an average of about 12 carbon atoms.

10. A lubricant composition comprising a major proportion of an oil of lubricating viscosity and from 0.5% to 5%, by weight, of an oil-soluble polyglycol substituted polymer of at least one monomer, said monomer containing a single polymerizable ethylenic bond and said polymer containing from about to about 96%, by weight, of hydrocarbon oil-solubilizing groups from said polymerized monomer and from about 4% to about by weight, of polyglycol groups, said oil-solubilizing groups being an aliphatic hydrocarbon group containing from 4 to 12 carbon atoms, said polyglycol group being a polyethylene glycol, said polymer being substantially saturated and having a total molecular weight of about 250,000 to about 1,000,000, said polyglycols having at least five alkylene oxide units each and being attached by a single thermally stable organic linking group to said polymer and from 0.8% to about 2.0%, by weight, of a lead salt of a dithiophosphoric acid of the formula 20 mol percent of a radical derived from oxodecyl alcohol.

References Cited in the file of this patent UNITED STATES PATENTS 2,364,283 Freuler Dec. 5, 1944 2,723,236 Asseff et al Nov. 8, 1955 2,892,783 Stuart et a1 June 30, 1959 Goldschmidt Apr. 26, 1960 

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTION OF AN OIL OF LUBRICATING VISCOSITY AND FROM 0.01% TO 10%, BY WEIGHT, OF AN OIL-SOLUBLE POLYGYCOL SUBSTITUTED POLYMER OF AT LEAST 1 MONOMER, SAID MONOMER CONTAINING A SINGLE POLYMERIZABLE ETHYLENIC BOND AND SAID POLYMER CONTAINING FROM ABOUT 14% TO ABOUT 96%, BY WEIGHT, OF HYDROCARBON OIL-SOLUBILIZING GROUPS FROM SAID POLYMERIZED MONOMER AND FROM 14% TO ABOUT 60%, BY WEIGHT, OF POLYGLYCOL GROUPS BEING SELECTED FROM THE CLASS CONBEING ALIPHATIC GROUPS CONTAINING AT LEAST 4 CARBON ATOMS, SAID POLYGLYCOL GROUPS BEING SELECTED FROM THE CLASS CONSISTING OF POLYALKYLENE GLYCOLS AND MONOALKYL ETHERS THEREOF HAVING FROM 2 TO 7 CARBON ATOMS IN EACH ALKYLENE GROUPS, SAID POLYMER BEING SUBSTANTIALLY SATURATED AND HAVING A TOTAL MOLECULAR WEIGHT OF AT LEAST 250,000, SAID POLYGLYCOLS HAVING AT LEAST FIVE ALKYLENE OXIDE UNITS EACH AND BEING ATTACHED BY A SINGLE THERMALLY STABLE ORGANIC LINKING GROUP TO SAID POLYMER AND FROM 0.3% TO 3%, BY WEIGHT, OF AN OIL SOLUBLE LEAD SALT OF A DITHIOPHOSPHORIC ACID OF THE FORMULA 